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Name Chemistry – Oxidation State homework We have learned that when compounds containing M(metals) and NM(nonmetals) are dissolved, the metal particles tend to form positively charged ions (cations), while non-metal particles tend to form negatively charged ions (anions). This is why water alone does not conduct electricity, but will if salt (NaCl for one) is dissolved in it. Importantly, when these same metal and non-metal particles are combined to form compounds they do not conduct electricity as solids. (How is this similar to the first compounds we saw, between sulfur and iron?) We will now examine the patterns that exist for the ratios in which these elements combine in order to determine the charges of the ions they form. This will help us think about oxidation states, and the behavior of electrons in orbitals. 1. Write the formula and draw the particle diagram for each compound. The ratio of ions in each compound is given. Atoms involved formula 1 calcium 1 oxygen 2 lithium 1 oxygen 2 aluminum 3 sulfur 2 boron 3 oxygen 1 magnesium 1 oxygen 2 sodium 1 sulfur 1 beryllium 1 sulfur particle diagram Atoms involved formula particle diagram Atoms involved formula 1 magnesium 2 chlorine 1 lithium 1 fluorine 1 beryllium 2 bromine 1 sodium 1 chlorine 1 calcium 2 bromine 1 aluminum 3 chlorine particle diagram Atoms involved formula particle diagram 1 boron 3 chlorine 2. Write each formula from Question 1 in the boxes corresponding to its elements. For example, the compound formed from sodium and sulfur have been written in the box for sodium and in the box for sulfur. Now add the rest. 1A 2A 3A 4A 5A 6A 7A Hydrogen 8A Helium 1 2 H He Lithium Beryllium 3 4 Boron Carbon Nitrogen Oxygen Fluorine Neon 5 6 7 8 9 10 Li Be B C N O F Ne Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon 11 12 P S Cl Ar Arsenic Selenium Bromine Krypton 33 34 35 13 14 Na2S NaCl Mg Al Si Potassium Calcium Gallium Germanium 19 20 K Ca 31 Ga 32 Ge 15 As 16 Se 17 Br 18 36 Kr 3. What patterns do you find in the formulas of the compounds formed in the table in #2? Based on these patterns, predict the formulas of the compounds formed by the ions below. Atoms involved ___ potassium ___ oxygen Ratio of ions in compound ___ calcium ___ gallium ___ sulfur ___ oxygen formula 4. How does a neutral atom become a positive ion? a negative ion? 5. Recall that in the electrolysis of water lab, hydrogen gas formed at the negative electrode. A) Based on this behavior, what must be the charge of hydrogen? B) Since hydrogen the smallest element, we will assign it a charge of +1. The other elements in the group 1A behave similarly enough to hydrogen, so we can assign them a charge of +1. Knowing how group 1A elements combine with other elements, you should be able to deduce the charges of elements in groups 2A, 3A, 6A and 7A. 6. Using the fact that compounds are also neutral, account for the fact that the ions combine in the ratios you have listed in the table in #2. Provide a couple of specific examples to support your explanation.
